Green Light Signal Downing Street - Boris Johnson

No 10 Downing Street Arch turns green ahead of COP26

10 Downing Street’s famous door has been lit up this evening to celebrate the UK hosting COP26, one of the biggest and most important climate change conferences of our time. The installation, made from energy efficient LED lights and sustainable materials, is based on National Grid’s Green Light Signal - a low-energy light bulb designed to glow green when electricity supply is cleanest.

Downing Street will shine green to highlight the cleaner energy powering Glasgow, where the conference is taking place.

Following the creation of the Green Light Signal, National Grid has today launched an app for mobile devices and a voice assistant skill across Amazon Alexa and Google Assistant which will put the power in consumers’ hands to use electricity when it is cleanest, and play their part in the fight against climate change. The new free-to-use tools  tell consumers the cleanest times to plug in alongside a full breakdown of the energy sources powering electricity in their region.

Prime Minister Boris Johnson says: “With COP26 just a few days away, I’m delighted to see Downing Street glowing green to mark our progress towards achieving a clean and reliable electricity system – supplying towns and cities across the country. 

“We can all do our bit to reach net zero carbon emissions, and the National Grid’s fantastic new app will help consumers power their homes and appliances with green, clean energy.”  

John Pettigrew, CEO of National Grid, says: “Climate change is the biggest challenge of our time. At a moment when world leaders, businesses and campaigners are in the UK for COP26, we are proud to show just how much greener, cleaner energy is powering Glasgow. Overall Great Britain’s energy system is becoming greener - in the last seven years we have cut carbon emissions from the electricity system by 66 per cent with clean energy like wind, solar and nuclear accounting for an average of 55 per cent of Britain’s electricity mix.

“By arming consumers with the facts about when their electricity is cleanest, we can show how every small action makes a difference to our planet.”

To illustrate how small individual steps can make a big difference in tackling climate change, National Grid has released figures showing how many tonnes of carbon could be saved if one million consumers went one step greener and plugged in the most common household appliances when their electricity was cleanest and greenest.

By using tumble dryers, which are very energy intensive, at cleaner and greener times, we could see a huge 164,250 tonnes of carbon saved, which is the equivalent to taking more than 78,000 cars off the road.[1]


Carbon Saved (tonnes)

Equivalent to how many cars we could take off the road:

Tumble Dryer



Washing Machine






Mobile phone charging



Lawn mower



Duncan Burt, Chief Sustainability Officer at National Grid, says: “We know that 70% of people believe individual efforts can make a difference in the fight against climate change, but they’re not always sure how to play their part. We want to make it as easy as possible for people to ask Alexa or check on their app to find out when their homes are powered by cleaner energy. By putting that information in their hands, we can help everyone take a small step towards changing their individual behaviour. Collectively, that could make a huge difference.”

To download the mobile app, android users can visit: and IOS users can visit

To activate the voice assistant skill, on the respective Alexa and Google platforms, simply search for the ‘National Grid’ skill and open by saying ‘Ask National Grid when to plug in’.

[1] Calculated impact if moving to the lowest emission hours and reduced emissions by 100g/kWh CO2.